1. Field of the Invention
This invention relates to backing tufted carpet with a novel thermoplastic composition to produce a composite product which has excellent sound absorbing characteristics and other properties useful in an automotive floor covering.
2. Prior Art
It is known to back size carpeting with thermoplastics containing ethylene/mono-unsaturated ester copolymers such as ethylene/vinyl ester or ethylene/alkyl acrylate copolymers. U.S. Pat. No. 3,645,949 of Crimi discloses applying to the back of carpeting a backing composition containing an ethylene/mono-unsaturated ester copolymer, an ethylene hydrocarbon polymer and optional additives such as wax and fillers. Other carpet backsizing compositions of this type are disclosed in U.S. Pat. No. 3,390,035 of Sands which discloses a backing composition containing ethylene/vinyl acetate copolymer, wax and various optional additives, and U.S. Pat. No. 3,583,936 of Stahl, which discloses a composition containing ethylene/vinyl ester, wax and a resin extender blend. U.S. Pat. No. 3,684,600 of Smedberg is directed to a backing system in which a precoat composition having an application viscosity of 2-2000 c.p.s. is applied prior to the main backing composition which has a higher application viscosity.
U.S. Pat. No. 3,745,054 of Smedberg relates to composition having a high filler content which is suitable for backsizing carpet. This composition comprises ethylene/vinyl ester copolymer, paraffin wax, microcrystalline wax, aliphatic thermoplastic hydrocarbon resin, dicyclopentadiene alkylation polymer, anti-oxidant and filler. Another carpet backsizing composition with a high filler content is U.S. Pat. No. 4,012,547 of Smedberg.
U.S. Pat. No. 3,982,051 of Taft et al. discloses a composition useful as a carpet backsizing which in addition to a copolymer of ethylene and an unsaturated ester such as ethylene/vinyl acetate, also contains polypropylene and a vulcanized rubber. U.S. Pat. No. 3,484,405 of Seto discloses adhesive compositions containing both rubber and ethylene/vinyl acetate but there is no indication that these particular compositions of this patent can be used as a carpet backing.
U.S. Pat. No. 3,645,948 of Stahl relates to backsizing compositions for carpets which are particularly useful where the backsized carpets are to be molded to a desired shape such as that of an automobile floor. The backsizing compositions contain 30 to 45 percent by weight of ethylene/vinyl ester copolymer and 55 to 70 percent by weight of a microcrystalline or Fischer-Tropsch wax.
As a means of decreasing the weight of automobiles, there have been recent efforts to prepare automotive carpets having a sound absorbing thermoplastic backing layer which eliminates the need for the sound absorbing materials previously located beneath the automotive carpets. In order to meet the requirements imposed by such use in an automotive carpet, the backing layer must: (1) Be moldable, including the ability to stretch during molding; (2) Be capable of locking carpet fibers into the carpet structure; (3) Withstand high temperature aging; (4) Have good low temperature cracking so that the carpet can be installed while cold; (5) Be capable of adhering to the material beneath the carpeting; (6) Have excellent sound absorbing properties, and (7) Be economical to produce. Additionally, it is preferred that the composition be readily admixed in an extruder.
One thermoplastic backing system for automotive carpets which has been developed utilizes a low viscosity ethylene/vinyl ester copolymer precoat followed by a heavier main coating consisting essentially of a higher viscosity ethylene/vinyl ester copolymer and filler. As a result of the stiffness of the main coating, there has been a problem of portions of the backed carpeting coming loose from the materials over which it is installed. This not only reduces the sound absorbing ability of the backed carpeting, but the loose carpeting rattles thereby contributing to the noise problem. Additionally, the main coating is relatively expensive and this has created an economic problem in view of the relatively thick coating which must be applied to obtain the desired sound absorbing characteristics.